We present
this individual for your consideration: She communicates in sign
language, using a vocabulary of over 1,000 words. She also
understands spoken English, and often carries on 'bilingual'
conversations, responding in sign to questions asked in English.
She is learning the letters of the alphabet, and can read some
printed words, including her own name. She has achieved scores
between 85 and 95 on the Stanford-Binet Intelligence Test.

She
demonstrates a clear self-awareness by engaging in self-directed
behaviours in front of a mirror, such as making faces or examining
her teeth, and by her appropriate use of self-descriptive
language. She lies to avoid the consequences of her own
misbehaviour, and anticipates others' responses to her actions.
She engages in imaginary play, both alone and with others. She has
produced paintings and drawings which are representational. She
remembers and can talk about past events in her life. She
understands and has used appropriately time-related words like
'before', 'after', 'later', and 'yesterday'.

She laughs at
her own jokes and those of others. She cries when hurt or left
alone, screams when frightened or angered. She talks about her
feelings, using words like 'happy', 'sad', 'afraid', 'enjoy',
'eager', 'frustrate', 'mad' and, quite frequently, 'love'. She
grieves for those she has lost- a favourite cat who has died, a
friend who has gone away. She can talk about what happens when one
dies, but she becomes fidgety and uncomfortable when asked to
discuss her own death or the death of her companions. She displays
a wonderful gentleness with kittens and other small animals. She
has even expressed empathy for others seen only in pictures.

Does this
individual have a claim to basic moral rights? It is hard to
imagine any reasonable argument that would deny her these rights
based on the description above. She is self-aware, intelligent,
emotional, communicative, has memories and purposes of her own,
and is certainly able to suffer deeply. There is no reason to
change our assessment of her moral status if I add one more piece
of information: namely that she is not a member of the human
species. The person I have described - and she is nothing less
than a person to those who are acquainted with her — is Koko, a
twenty-year-old lowland gorilla.

For almost
twenty years, Koko has been living and learning in a language
environment that includes American Sign Language (ASL) and spoken
English.[1]
Koko combines her working vocabulary of over 500 signs into
statements averaging three to six signs in length. Her emitted
vocabulary — those signs she has used correctly on one or more
occasions - is about 1,000. Her receptive vocabulary in English is
several times that number of words.

Koko is not
alone in her linguistic accomplishments. Her multi-species
'family' includes Michael, an eighteen-year-old male gorilla.
Although he was not introduced to sign language until the age of
three and a half, he has used over 400 different signs. Both
gorillas initiate the majority of their conversations with humans
and combine their vocabularies in creative and original sign
utterances to describe their environment, feelings, desires and
even what may be their past histories. They also sign to
themselves and to each other, using human language to supplement
their own natural communicative gestures and vocalisations.

The results of x2 tests (1 df) indicate that Koko's
performance on the ACLC in all modes and at all levels of
difficulty was significantly better than chance, and that there
was no significant difference in her comprehension whether the
instructions were given in sign, English or sign plus English.

Sign language
has become such an integral part of their daily lives that K-oko
and Michael are more familiar with the language than are some of
their human companions. Both gorillas have been known to sign
slowly and repeat signs when conversing with a human who has
limited signing skills. They also attempt to teach as they have
been taught. For example, one day Michael had been repeatedly
signing 'chase'
(hitting two fisted hands together) but was getting no response
from his companion, who did not know this sign. He finally took
her hands and hit them together and then gave her a push to get
her moving. Similarly, Koko has often been observed moulding the
hands of her dolls into signs.

Tests have
shown that the gorillas understand spoken English as well as they
understand sign. In one standardised test called the Assessment of
Children's Language Comprehension, novel phrases corresponding to
sets of pictures were given to the gorillas under conditions in
which the tester did not know the correct answers. Koko's
performance (see Table 1) was twice as good as might have been
expected by chance, and there was no significant difference in her
performance whether the instructions were given in sign only or in
English only.[2]

Table 2
Koko's tested IQ 1975-6

Date

Test

CA*

MA+

IQ‡

Dec 1976

Khulman—Anderson

65

56

84.8

July 1976

Peabody Picture Vocabulary Test

60

49

81.6

Jan 1976

Stanford—Binet Intelligente Scale

54

46

85.2

Nov 1975

Wechsletr Preschool and Primary Scale of Intelligence

51

37

71.0

July 1975

Stanford—Binet

48

44

91.7

Apr 1975

McCarthy Scales of Children’s

45

32

73.0

Feb 1975

Stanford--Binet

43

37

86.0

* Chronological age in months.

+ Mental age in months

‡ The McCarthy GCI stands for General Cognitive Index and is a
scaled score, not a quotient.

Because the
gorillas understand linguistic instructions and questions, we have
been able to use standardised intelligence tests to further assess
their abilities.[3]
Koko's scores on different tests administered between 1972 and
1977 yielded an average IQ of 80.3 (see Table 2). More significant
than the actual scores is the steady growth of Koko's mental age.
This increase shows that she is capable of understanding a number
of the principles that are the foundation of what we call abstract
thought.

Many of those
who would defend the traditional barrier between Homo sapiens
and all other species cling to language as the primary
difference between humans and other animals. As apes have
threatened this last claim to human uniqueness, it has become more
apparent that there is no clear agreement as to the definition of
language. Many human beings - including all infants, severely
mentally impaired people and some educationally deprived deaf
adults of normal intelligence -fail to meet the criteria for
'having language' according to any definition. The ability to use
language may not be a valid test for determining whether an
individual has rights. But the existence of even basic language
skills does provide further evidence of a consciousness which
deserves consideration.

Conversations
with gorillas resemble those with young children and in many cases
need interpretation based on context and past use of the signs in
question. Alternative interpretations of gorilla utterances are
often possible. And even if the gorillas' use of signs does not
meet a particular definition of language, studying that use can
give us a unique perspective from which to understand more
directly their physical and psychological requirements. By
agreeing on a common vocabulary of signs we establish two-way
communication between humans and gorillas. We can learn as much
from what they say as we can by evaluating how they say it.

Some of what
they tell us can be anticipated: 'What do gorillas like to do
most?' 'gorilla love eat
good'. Or, 'What makes you happy?'
'gorilla tree'. 'What
makes you angry?' 'work'.
'What do gorillas do when it's dark?'
'gorilla listen
[pause], sleep'. Some
responses, on the other hand, are quite unexpected: 'How did you
sleep last night?' (expecting
'fine' 'bad' or some
related response). 'floor
blanket' (Koko sleeps on the floor with blankets). 'How do
you like your blankets to feel?'
'hot koko-love'.
'What happened?' (after an earthquake).
'darn darn floor bad bite.
trouble trouble'.

Gorillas have
suffered from a reputation for aloofness, low level of motivation
and a contrary nature. Such gorilla stubbornness and negativism
have been encountered and documented in our work with Koko and
Michael, but certain findings indicate that this is evidence of
intelligence and independence rather than of stupidity. And it is
just this ornery independence that seems to spark episodes of
humour and verbal playfulness. A characteristic incident involved
Koko and assistant Barbara Hiller. Koko was nesting with a number
of white towels and signed,
'that red', indicating one of the towels. Barbara corrected
Koko, telling her that it was white. Koko repeated her statement
with additional emphasis, 'that red'. Again Barbara stated that the towel was
white. After several more exchanges, Koko picked up a piece of red
lint, held it out to Barbara and, grinning, signed,
'that red'.

Our approach
has been to give Koko and Michael vocabulary instruction but no
direct teaching of any other language skill. Most of the signs
were learned either through the moulding of the gorillas' hands
into signs or through imitation. But Koko and Michael have both
created signs and used the language in diverse ways not explicitly
taught. In a very real sense, the study has involved the mapping
of skills, rather then the teaching of skills. This mapping is
being done through observations in relatively unstructured and
uncontrolled situations and through rigorous tests. The best
possible linguistic and cognitive performances are likely to be
given in the informal setting, with support coming from tests.

The gorillas
have taken the basic building block of conversation (signs) and,
on their own, added new meaning through modulation, a grammatical
process similar to inflection in spoken language. A change in
pitch or loudness of the voice, or the addition (or substitution)
of sounds, can alter the meaning of a spoken word. In sign
language this is accomplished through changes in motion, hand
location, hand configuration, facial expression and body posture.
The sign bad, for
instance, can be made to mean 'very bad' by enlarging the signing
space, increasing the speed and tension of the hand, and
exaggerating facial expression. Koko, like human signers, has
exploited this feature of sign language to exaggerate a point, as
when she signed thirsty
from the top of her head to her stomach, instead of down
her throat.

The gorillas
have been observed to use these kinds of variations to mark
relations of size (e.g. small versus large
alligator sign),
number (birds versus
bird by repeating the
sign), location
(scratch-on-back), possession (KoKo's-BABY signed
simultaneously), manner, degree, intensity or emphasis
(tickle signed with
two hands), agent or object of an action
(you-sip signed by
moving the signing hand toward the intended agent), negation
(negating the attention
sign by changing its location), to express questions
(through eye contact and facial expression) and as a form of word
play akin to wit or humour (simultaneously signing
sad frown when asked
to 'smile' for the camera).

A
conversation with Koko that involved this kind of creativity with
the sign rotten has
been documented on film. Koko demonstrated the standard form of
the sign in an exchange of insults after her companion called her
a stinker. Koko then
inflected the sign by using two hands (perhaps meaning 'really
rotten') and in the same sequence, brought the sign off her nose
toward her companion, conveying the idea 'you're really rotten'.
Koko's use of rotten
in this conversation also demonstrates her grasp of the
connotation of a word rather than its denotation or concrete or
specific meaning.

The meaning
of the gorillas' signs are not necessarily identical to the most
common meanings, and in some cases they are entirely different. To
interpret the gorillas' conversations correctly, one must discover
what the signs mean to them. Word-association games provide some
clues. The gorillas are asked, 'What do you think of when I
say-------?'

Examples of
stimulus-response pairs from sessions with Michael include:
teacher-hand, michael-foot,
and similarly,
afraid-hug, ^ad-stink and
hungry-eat. The
gorillas have also simply been asked to give
definitions. Examples from data on Koko follow:

There are
also words that Koko does not understand, and she sometimes
corrects her companions when they apply them to her: on Christmas
Eve in 1984 Koko picked up the telephone, listened to the dial
tone, then signed 'ron'
and handed the receiver to Barbara Hiller. When another
companion commented, 'She's a goofball!' Koko responded,
'no, gorilla'. She
has given similar responses when referred to as a 'juvenile' or a
'genius'.

Another way
Koko and Michael have created novel meanings for basic vocabulary
signs is through an unusual coining process in which they employ
signs whose spoken equivalents match or approximate the sounds of
English words for which no signs have been modelled. For example,
Koko uses a modulated knock sign to mean 'obnoxious'. This
indicates that she knows:

1. That the
sign knock is
associated with the spoken word 'knock'.

2. That
'knock' sounds like the spoken word 'obnoxious'.

3. That the
sign knock can
therefore be applied semantically to mean something or someone
obnoxious.

Other
examples include the substitution of the sign
tickle for 'ticket',
skunk for 'chunk',
and lip stink for
'lipstick'. When Michael was asked to 'say bellybutton', he first
signed 'bellybutton'
(pointing to it), then signed
'berry bottom'.

When signs
have been repeatedly demonstrated that are difficult or impossible
for Koko to form, her solution has often been to make restitutions
based on the sound of the corresponding English word:
nee for 'need',
red for 'thread',
lemon for 'eleven',
and bird for ‘word’.

The gorillas
also communicate new meanings by making up their own entirely new
signs. The intended meanings of some of the gorillas' invented
nouns have been obvious ('nailfile', 'eyemakeup', 'barrette')
because of their iconic form. The meanings of more abstract words
such as verbs and prepositions ('above', 'below', 'take-off), have
to be worked out over time from records of the situations in which
they occurred.

An analysis
of the 876 signs emitted by Koko during the first ten years of the
project[4]
revealed that fifty-four signs, 6 per cent of her total emitted
vocabulary, were her own inventions. Another 2 per cent (fifteen
signs) were compounded by Koko from signs she was taught.
Originally, only ten signs (1 per cent) were counted as natural
gorilla gestures. New data from detailed observations of the
gestures used by uninstructed gorillas indicates that these
categories are fluid, and some of Koko's inventions are shared by
other gorillas.

These
invented signs indicate that the gorillas, like human children,
take initiative with language by making up new words and by giving
new meanings to old words. On the next level, there is evidence
that Koko and Michael can generate novel names by combining two or
more familiar words. For instance, Koko signed
'bottle match' to
refer to a cigarette lighter,
'white tiger' for a
zebra, and 'eye hat'
for a mask. Michael has generated similar combinations, such as
'orange flower sauce' for nectarine yogurt and
'bean ball' for peas.
Other examples in the samples of the gorillas' signing are
'elephant baby' for a
Pinocchio doll and 'bottle
necklace' for a six-pack soda can holder. Critics have
commented that such phrases are merely the pairing of two separate
aspects of what is present. Many of the above examples, however,
cannot be explained in this way - when Koko signed
'bottle match',
neither a bottle nor a match was present.

The gorillas
have applied such new descriptive terms to themselves as well as
to novel objects. When angered, Koko has labelled herself a
'red mad gorilla'.
Once, when she had been drinking water through a thick rubber
straw from a pan on the floor after repeatedly asking her
companion for drinks of juice which were not forthcoming, she
referred to herself as a
'sad elephant'.

Intrigued by
examples of language use such as these, we went on to obtain more
empirical evidence of the gorillas' metaphoric capacity. Koko was
given a test devised by Howard Gardner[5]
in which she was asked to assign various descriptive words to
pairs of colours. The adjective pairs used were 'light-dark',
'happy-sad', 'loud-quiet', 'hard-soft’, and 'warm-cold'. In
videotaped sessions administered under conditions in which Koko
could see only the stimulus and not the experimenter, she had no
difficulty identifying literal dark versus light (two shades of
green), red (versus blue) as warm, brown (versus blue-grey) as
hard, violet-blue (versus yellow-orange) as sad, and lemon yellow
(versus spring green) as loud. Koko indicated her answers either
by pointing or by verbal descriptions (e.g.
'orange that fine',
when asked which colour was happy). Ninety per cent of her
responses were metaphoric matches as determined by Gardner and by
three project research assistants who took the same test.
Preschoolers in Gardner's study made only 57 per cent metaphoric
matches; seven-year-olds, 82 per cent.[6]

Another
creative aspect of the gorillas' language behaviour is humour.
Humour, like metaphor, requires a capacity to depart from what is
strictly correct, normal or expected. For example, when asked to
demonstrate her invented sign for
stethoscope for the
camera, Koko did it on her eyes instead of on her ears. Asked to
feed her chimp doll, she put the nipple to the doll's eye and
signed 'eye'.
Appreciation of this kind of wit is sometimes dependent on
recognising the sign behind the distortion. A sceptic might see
this as a simple error, but in the case of signs that the gorillas
themselves invent, such as
stethoscope, this is not likely, and there are
consistencies that run across the gorillas' humorous use of signs.

We have often
noticed Koko giving an audible chuckling sound at the result of
her own and her companions' discrepant statements or actions. She
discovered that when she blew bugs on her companions, a
predictable shrieking and jumping response could be elicited.
Originally, she laughed at this outcome, but now she chuckles in
anticipation of the prank as well. Accidents and unexpected
actions by others can also cause Koko to laugh. Chuckles were
evoked, for instance, by a research assistant accidentally sitting
down on a sandwich and by another playfully pretending to feed
sweets to a toy alligator. Developmental psychologists have found
that the earliest form of humour in young children,
incongruity-based humour, relies on similar principles of
discrepancy applied to objects, actions and verbal statements.

Koko has also
made verbal 'jokes'. On 30 October 1982, Barbara Hiller showed
Koko a picture of a bird feeding her young.

K:
that me [to the adult
bird].

B: Is that
really you?

K:
koko good bird.

B: I thought
you were a gorilla.

K:
koko bird.

…

B: Can you
fly?

K:
good. [good can mean
yes.]

B: Show me.

K: FAKE BIRD,
CLOWN. [Koko laughs.]

B: You're
teasing me. [Koko laughs.]

B: What are
you really?

Koko laughs
again, and after a minute signs

K:
gorilla koko.

In stark
contrast to the gorillas' ability to express humour is their
ability to communicate their thoughts and feelings about death.
When Koko was seven, one of her teachers asked, 'When do gorillas
die?' and she signed,
'trouble, old.' The teacher also asked, 'Where do gorillas
go when they die?' and Koko replied,
'comfortable hole bye.'
When asked 'How do gorillas feel when they die - happy,
sad, afraid?' she signed,
'sleep'. Koko's reference to holes in the context of death
has been consistent and is puzzling since no one has ever talked
to her about burial, nor demonstrated the activity. That there may
be an instinctive basis for this is indicated by an observation at
the Woodland Park Zoo in Seattle, Washington. The gorillas there
came upon a dead crow in their new outdoor enclosure, and one dug
a hole, flicked the crow in, and covered it with dirt.[7]

In December
of 1984 a tragic accident indicated the extent to which gorillas
may grieve over the death of their loved ones. Koko's favourite
kitten, All Ball, slipped out of the door and was killed by a
speeding car. Koko cried shortly after she was told of his death.
Three days later, when asked, 'Do you want to talk about your
kitty?' Koko signed, 'cry'.
'What happened to your kitty?' Koko answered,
'sleep cat'. When she
saw a picture of a cat who looked very much like All Ball, Koko
pointed to the picture and signed,
'cry, sad, frown'.
Her grief was not soon forgotten.

17 March
1985, with Francine Patterson

F: How did
you feel when you lost Ball?

K:
want.

F: How did
you feel when you lost him?

K: OPEN
TROUBLE VISIT SORRY.

F: When he
died, remember when Ball died, how did you feel?

K: RED RED
RED BAD SORRY KOKO-LOVE GOOD.

Arthur Caplan
argues that animal interests and human interests lould not be
counted equally, claiming that nonhuman animals lack rtam traits
that make a moral difference. He uses the following sample to
illustrate his point:

If you kill
the baby of a baboon the mother may spend many weeks looking for
her baby. This behaviour soon passes and the baboon will go on to
resume her normal life. But if you kill the baby of a human being
the mother will spend the rest of her life grieving over the loss
of her baby. Hardly a day will go by when the mother does not
think about and grieve over the loss of her baby.[8]

But in this
example the comparison is between outward behaviour in the case of
the baboon mother, and a private mental state in the case of the
human mother. In most such cases, the human mother also resumes
her normal life: returning to her workplace, caring for her other
children, going about her daily activities as before. Her grief is
not necessarily apparent to the casual observer. Because the
baboon mother cannot (or chooses not to) communicate to us
her internal feelings about the death of her baby, it is assumed
that it does not matter to her. While we cannot make any claims
here about the emotional life of baboons, we have considerable
evidence that Koko continues to mourn the loss of her adopted
'baby', All Ball, even years after his death.

19 March
1990

Koko comes
across a picture of herself and All Ball in a photo album.

K: THAT BAD
FROWN SORRY [emphatic] UNATTENTION.

Through
conversations such as these the gorillas show not only that they
are capable of experiencing emotions, but that they are aware of
their emotions and can use language to describe them. Koko, at age
six, was given a test that parallels a study with human children
five to thirteen years old by Wolman, Lewis and King.[9]
Koko was asked a series of questions with these frames:

(1) Do you
ever feel_____?

(2) When
do you feel.

The target
feeling states were anger, fear, happiness, sadness, hunger,
thirst, sleepiness and nervousness. Like the younger human
subjects, Koko most frequently reported external events as
conditions of emotional arousal; for example, when asked, 'When do
you feel hungry?' she answered,
'feel time'. A
possible explanation of this reply is that when it is time (to
eat), she feels hungry. Koko regularly uses an emphatic
time sign to tell her companion to bring out the next
scheduled meal. Her replies to questions about anger seem to be
related to events of the months preceding the test. Her responses
to 'When do you feel mad?' included
'koko love marjie bye'
and 'koko mad girl'-
At the time this test was given Koko had been having a
difficult time with a new assistant named Marjie.

Koko has
displayed a capacity for empathy in her comments about the
emotional states of others:

24
September 1977

Koko is shown
a picture of the albino gorilla Snowflake struggling against being
bathed. Koko signs 'me cry
there', indicating the picture.

3 November
1977, with companion Cindy Duggan

Koko looks at
a picture of a horse with a bit in his mouth.

K:
horse sad.

CD: Why?

K: TEETH.

27
December 1977

Michael has
been crying because he wants to be let out of his room. Koko, in
the next room, is asked how Michael feels.

K: FEEL SORRY
OUT.

7 April
1986

Mitzi
Phillips tells Koko about a problem that is making her feel sad.

MP: What
could I do to feel better?

K: CLOSE
DRAPES . . . TUG-OF-WAR.

As Mitzi
writes in the diary, Koko quietly comes up to her.

K:
sad? [Making the sign
a question by raising her eyebrows and

leaning
forward, a standard ASL question form.]

MP: I feel
better now.

Koko smiles.

The gorillas
have also been asked to represent feeling states such as love,
hate, happiness and anger with paints on canvas. Given free choice
of ten or more colours, the gorillas produced works of contrasting
colour and form. Asking them to paint emotions seemed a reasonable
request because they had earlier demonstrated some primitive
representational ability in their drawings and paintings done from
models or from memory. Both Koko and Michael titled these works
appropriately. One example of Michael's representational art is a
work he called apple chase',
for which he used our black and white dog named Apple as a
model. The black and white painting bears a resemblance to Apple's
head. (It is interesting to note that Michael and Apple have a
special relationship. They frequently play 'chase' together, and
Michael often initiates the game by signing
chase to Apple.)

Michael
frequently expresses himself creatively through sound play. He
uses various objects and parts of his body to produce a wide
variety of sounds and intricate rhythms. In creating his 'sound
tools' he experiments with different materials in his environment.
In addition to rhythmic drumming and tapping, for example, he
sometimes strums a rope or fabric strip held taut between his feet
and his mouth. He made a rattle by filling a PVC pipe end with
hard nutshells and shaking it vigorously with his hand covering
the open end. Then he filled his mouth with the nutshells and
shook them around, making a contrasting 'wet' rattling sound.

Koko
regularly expresses her creativity through fantasy play, alone or
with her companions. Often this play involves her plastic reptile
toys and centres on their tendency to 'bite'.

13 October
1988, with Mitzi Phillips

Koko is lying
down with one of her toy alligators. She looks at it and signs
'teeth'. She examines
its mouth. She kisses it, puts two alligators together as if to
make them kiss each other, then gives them a three-way kiss. She
puts her hand into the toy's mouth, then pulls it out and shakes
her hand.

MP: Oh, did
it bite you?

K:
bite.

MP: Oh, no!
Does it hurt?

Koko kisses
her finger.

MP: May I see
that bad alligator?

Koko gives it
to Mitzi. Mitzi 'asks' the alligator why it bit Koko and pretends
to listen to its answer, then hands it back to Koko.

Koko kisses
the toy again and again.

K: ALLIGATOR.
GORILLA. BITE. GORILLA NUT NUT NUT. STOMACH TOILET.

They are
intelligent and emotional, they express themselves creatively
through language, art, music and fantasy play; but are gorillas
self-aware? Once considered unique to human beings, self-awareness
is an elusive concept. Its many definitions are both varied and
vague, although almost everyone has some notion of what it means.
Through their signing, Koko and Michael have shown a number of
generally accepted cognitive correlates of self-awareness,
including the use of personal pronouns, references to their own
internal and emotional states, humour, deception and
embarrassment.

While
self-awareness is probably best determined through the use of
language, self-recognition in mirrors is an accepted indicator of
self-awareness in human infants and other nonverbal individuals.
In formal mirror-marking tests, the subjects are first exposed to
a mirror and observed for any self-directed behaviour. Then their
appearance is altered in such a way that they can only detect the
change with the aid of mirror. Nonhuman primates undergoing these
tests are normally anaesthetised and marked on the face with red
dye. Human children are marked surreptitiously with a spot of
rouge while they are distracted. Once marked, subjects are again
exposed to a mirror. Touching the mark while looking in the mirror
is considered confirming evidence of self-recognition.
Chimpanzees, orang-utans and humans have demonstrated a capacity
for self-recognition in mirror tests, but the six gorillas
previously tested failed to do so. It was concluded that gorillas
lacked the cognitive capacity for self-awareness, in spite of
informal reports to the contrary.

We gave a
comparable mirror test to Koko[10]
in which she demonstrated for the first time that gorillas, too,
are capable of mirror self-recognition. For Koko, we used a
modified procedure so that she would not have to be anaesthetised.
During a series of ten-minute sessions videotaped over a three-day
period, Koko's brow was wiped with a warm, damp, pink washcloth.
During one of these sessions, the washcloth had been dipped in
clown paint of the same pink colour. In the sessions in which she
was unmarked, Koko touched the target area an average of only one
time per session. During the fifth session when her brow was
marked, she touched the target area forty-seven times, only after
viewing it in the mirror. As she attempted to remove the paint,
she also spent the most time viewing her reflection during the
session in which she was marked. It is evident that Koko
recognised the altered image as her own.

Koko had
previously passed an informal 'mark test' when she attempted to
rub away a dark spot of pigment on her upper gum, a spot that she
had precisely located by looking into her mouth with a mirror.
Captured on videotape, this spontaneous experiment of nature
eliminated any possibility that Koko sensed the presence of the
mark before noticing it in the mirror.

Why did the
other gorillas fail to pass the mirror test? There are a number of
possible explanations, including their age, rearing histories and
social situations, their individual sensitivity to anaesthesia, or
lack of motivation. There may also have been methodological
problems, as at least two of the subjects touched the mark before
exposure to the mirror. However, a more likely explanation is that
the gorillas were inhibited by the presence of unfamiliar
observers. Primatologists who have worked closely with gorillas
have long been aware that the presence of strangers can profoundly
affect gorilla behaviour, and this has been our experience as
well. In certain situations Koko and Michael show a sensitivity to
being watched even by familiar companions. Ironically, it may have
been the gorillas' very capacity for self-consciousness that
prevented them from exhibiting behaviours indicative of
self-recognition in the test situation.

Mirrors have
been part of Koko's environment from her infancy. At the age of
about three and a half, Koko began to exhibit self-directed
behaviours in front of a mirror. She would groom her face and
underarms, pick at her teeth and examine her tongue while studying
her reflection. She would also comb her hair, make faces and adorn
herself with hats, wigs and make-up. Michael has exhibited similar
behaviours, which have been documented on videotape, even though
his exposure to mirrors has been much more limited. These
mirror-guided behaviours are normally exhibited by human children
by the time they are two years old. Before that age children
respond to their mirror image as they would to another child.

We took
advantage of Koko's linguistic abilities to cross-validate the
evidence of self-awareness provided by her response to mirrors.
Two 'Who are you?' questions were asked during each of the first
four test sessions while Koko was away from the mirror. After the
fifth (marking) session Koko was asked this question once more
while away from the mirror, and also 'Who is that?' of her mirror
reflection. Although correct answers to these questions can simply
be learned responses, the data argue otherwise in Koko's case. Her
responses (listed in Table 3) were all different, multi-sign
utterances, but had one consistent theme. Each reply to the
questions contained one or more of the three signs:
'gorilla', 'me', 'koko'.
Koko does not use these three words in response to all
'who' questions. When asked 'who' questions about her closest
companions, her responses were different for each individual but
consistent over repeated questions about each individual.

Human
children begin by using personal pronouns and self-referents in
their speech at about the same time that they begin to recognise
themselves in mirrors. Similarly, at the same age that she began
to exhibit self-directed behaviours in front of a mirror, Koko
acquired the signs for 'me', 'mine', 'myself, 'you', and proper
nouns, including 'Koko'. The gorillas have also demonstrated
self-awareness in their ability to describe themselves as the same
as or different from others. For example, research assistant
Maureen Sheehan questioned Koko about the differences between
gorillas and humans:

Table 3 Koko's responses to self-identity questions

Test
session

First
Response

Second
Response

‘Who are
you?’

1

Me gorilla nipples tickle

Nipples gorilla

2

Polite-Koko Koko nut nut polite

Polite devil hair head Jojo sweet bad

3

Koko polite me thirsty

Gorilla me

4

Polite me thirsty feel Koko-love

Polite polite-Koko Koko feel thirsty sorry

5

Koko polite sorry good

Koko; please gimme brow-wiper

‘who is
that?’ (to mirror)

5

Me there Koko good teeth good

MS: What's
the difference between you and me?

K:
head.

MS: And how
are our heads different?

Koko beats on
her head with her open hands quite hard, harder than a human would
ever do.

MS: What else
is different between us?

Koko moves
her hand up to her stomach, a gesture resembling BLANKET.

MS: Do you
mean something about your stomach?

K: STOMACH
GOOD THAT.

MS: Oh, but
what were you saying about blanket, different?

Koko moves
her hands up and down her torso, then pulls the hair on her belly.
Maureen interprets these new gestures as meaning 'body hair'.

MS: Now can
you name something the same?

K:
eye.

MS: Yes,
that's right, we both have eyes.

K:
love.

Michael was
once asked a related question: 'What makes you different from your
cat?' He responded, 'gorilla
me mike'.

Self-awareness is also shown by the gorillas when they talk about
themselves in situations removed in space or time from the current
one. This capacity for displacement is clearly and repeatedly
demonstrated in conversations such as the following:

10 July
1984, with Frandne Patterson, six days after Koko's birthday

F: What
happened on your birthday?

K:
sleep eat.

F: Didn't
something special happen on your birthday?

K: OLD
GORILLA.

F: Yes,
you're thirteen years old and big.

Michael began
at an early age to tell stories about past events. In 1979, when
the project was still located on the Stanford University campus,
the gorillas witnessed a violent, screaming argument between a
red-haired woman and a research assistant at a nearby laboratory
building. The woman apparently hit the assistant and had to be
subdued at gunpoint by the police. When Michael's companion
Barbara Weller arrived, knowing nothing of the incident, she found
him at the window.

M:
girl.

Michael
stares out of the window for a few more minutes.

M: KNOW
HIT-IN-MOUTH.

B: Know
hit-in-mouth?

M:
HIT-IN-MOUTH RED BITE.

B: Why are
you signing hit-in-mouth?

M:
know.

B: Who do you
want to hit-in-mouth?

M: HAIR GIRL
RED.

B: What? Red
hair girl?

M:
lip [The gorillas use
lip to mean 'woman'.]

B: Lip?

M: LIP LIP
LIP BIG-TROUBLE.

Michael Lewis[11]
suggests that there are certain emotional states that only the
self-aware can have. One such state is embarrassment. In order to
be embarrassed animals must be capable of reflecting on their own
behaviour and comparing it to standards set by society or
themselves. Koko seems embarrassed when her companions notice that
she is signing to herself, especially when the signing involves
her dolls. One incident recorded when Koko was five years old
provides an example. Her companion observed her creating what
appeared to be an imaginary social situation between two gorilla
dolls. She signed, 'bad, bad' while looking at one doll, and
'kiss' while looking
at the other. Next, she signed,
'chase, tickle', hit
the two dolls together, and then wrestled with them and signed,
'good gorilla, good good'.
At this point she noticed that she was being watched and
abruptly put the dolls down.

There is no
reason to think that Koko and Michael are significantly different
from other gorillas in their inherent linguistic capacities,
self-awareness or other mental abilities. They are two individuals
selected more or less at random from the total population of
gorillas, and the circumstances of their first few years were very
different. So it is fair to assume that they are representative of
their species. Nor is there reason to consider them essentially
different from other gorillas because of their experience with
human language. Indeed, a few zoo gorillas who have been exposed
informally to sign language have shown that they, too can learn
signs, even later in life and without intensive teaching. By
teaching sign language to Koko and Michael we have not imposed an
artificial system on them, but rather have built upon their
existing system to provide a jointly understood vocabulary for
mutual exchange. Detailed observation and analysis of the
communicative gestures used by 'uninstructed' gorillas in a zoo
group indicate that their own gestural communication system is
much more complex then previously thought,[12]
This ongoing study involves analysing a videotape compilation of
these gestures and classifying them according to context and
apparent functions. The gorillas have been observed to use
communicative gestures in the following contexts: play invitation,
anticipatory play reaction, play inhibition, indication of play
location and action, sexual activities, agonistic interaction,
group movement, body positioning and solitary play. One type of
gesture involves touching to position the body of another, usually
in the context of sexual activity. Another significant type of
gesture uses the hands for deception, for example to hide a
'playface' grin in order to alter the signal being received by
another gorilla. So far, over forty apparently discrete and
meaningful gestural types have been identified in one five-member
population. Gorillas in this particular group have been observed
using conversational strings of up to eight gestures, and there
seems to be an element of request and response in their dialogues.

While we are
a long way from any comprehensive understanding of natural gorilla
communication, it is clear that non-signing gorillas use gestures
to communicate with one another. Field researchers may not have
always recognised the significance of semantic gestures used by
tree-living gorillas, because they were unfamiliar with the
gorillas' communicative habits or with gestural communication in
general, or because the presence of human observers inhibits the
gorillas' normal behaviour. Recognition of semantically
significant gestures and sounds becomes easier as we become more
familiar with gorillas as communicators.

Perhaps our
most interesting findings relate to how astonishingly like us
gorillas are - or how like them we are. But the striking
similarities between gorillas and humans are hardly surprising in
light of the most recent studies of our genetic kinship. The
scientific classification of living organisms is based on the
apparent similarities between those organisms. Within the order
Primates, human beings have always been set apart in a separate
family. More recent studies involving comparisons of chromosomes
and analysis of DNA leave little doubt that apes and humans should
be classed together in the family Hominidae. Some
researchers now propose that humans, gorillas and chimpanzees also
belong in the same subfamily, though the arrangement within this
subfamily is still to be determined.[13]

Through what
they have taught us about gorillas, Koko and Michael are helping
to change the way we view the world. They force us to re-examine
the ways we think about other animals. With an emotional and
expressive range far greater than previously believed, they have
revealed a lively and sure awareness of themselves as individuals.
Asked to categorise herself, Koko declared
'fine animal gorilla'. Indeed. Fine animal-persons, gorillas.